Carrier-current protective-relaying and telemetering system



1945' J. L. BLACKBURN ET AL 2,367,921

CARRIER-CURRENT PROTECTIVE-RELAYING AND TELEMETERING SYSTEM Filed Dec. 8, 1942 TV 252 (SP 2/ Rec.

T V 1P2 R3 R E A H WlTNESSESz' 4 INVENTORS James f'TC/mpman and I V B/aCkbUF/L ATTORNEY Patented Jan. 23, 1945 UNITED STATES PATENT OFFICE CARRIER-CURRENT PROTECTIVErRELAY- INC AND TELEMETERING SYSTEM John L. Blackburn and James F. Chapman, East Orange, N. J assignors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application December 8, 1942, Serial No. 468,226

3 Claims. (01. 175 -294) Our invention relates to carrier-current protective-relaying systems for protecting transmission lines against faults, and it has particular relation to improvements in the use of the carrier-current channel for other uses other than protective relaying, especially for modern high-rate telemetering-equipment over the carrier-current channel, which requires carrierstarting-and stopping switching-operations as often as 40 to 200 or more times a minute, which imposes a rather considerable burden on this carrier-control telemetering switching equipment.

The particular object of our invention is to cope with the problem of auxiliary contactorswitches or other auxiliary protective relays which usually have to be energized at the same time when the carrier-current transmitter is energized as a result of the operation of one of the carrier-starting fault-detector relays. These carrier-starting fault-detecting relays are extremely sensitive in operation, and hence their contact-elements are as light in weight as possible. The auxiliary contactor-switches are needed, not only for the purpose of by-passing the light fault-detector contacts and thus relieving them from their current-carrying duty, and providing a firm, non-chattering carrier-controlequipment operates only at times of systemfaults, which are of rare occurrence, and since the fault-protecting operation usually lasts for only a very few cycles, it will be apparent that the almost constantly operated telemetering carrier-controlling switching equipment is called upon to carry a heavy additional burden, in energizing and deenergizing this auxiliary protective relaying-equipment in parallel with the transmitter-controlling circuits, so much so, that the life of the telemetering keying-equipment has been very greatly reduced. Nevertheless, this ling contact, but usually also for providing additional contacts responsive to the fault-detection, these additional contacts being utilized for vari ous protective-relaying purposes such as controlling the energization of a timer-switch for back-up-protection, or providing various interlocks sometimes needed in protection against outof-step system-operation, The auxiliary contactor-switches also serve another function in interposing a slight delay in the removal of carrier-current transmission after the dropping out of the fault-detector, thus providing a small but important time-hesitation which is extremely useful, and all but necessary, in properly coordinating the various relaying times upon the clearance, or partial clearance, of a fault-condition on the protected transmission-line.

Heretofore, in a common type of carrier-current protective-relaying equipment, the operating-circuits of these auxiliary contactor-switches or other auxiliary protective relays have been energized, in parallel with the transmitter-starting circuit, whenever carrier-current transmission has been initiated, either as a result of a fault-detector operation or during the operation of the telemetering equipment or other other uses equipment.

Since the protective-relaying situation has been endured heretofore, becauseof the necessity for having the auxiliary relaying equipment instantly available for operation in the event of a fault on the transmission system.

It is a more specific object of our invention to provide auxiliary relaying-means, which is energized responsively to the fault-detector response of the protective relaying-apparatus, without imposing any material burden on the telemetering key, for disconnecting the energizing-circuits of these auxiliary protective relays, except in the event of a fault-detector response. In this manner, the telemetering key is protected against having to constantly handle the energizing-currents for these auxiliary protective relays, with a single exception which occurs when the telemetering key is being operated at the same instant when there is a fault on the transmission line, in which event the burden on the telemetering key is'increased', by the amount of current drawn by the auxiliary relaying equipment, but this increased burden will endure only for a very short period of time, whichwill not greatly reduce the life of the telemetering key.

An exemplary form of embodiment of our invention is shown in the drawing, wherein:

Figure 1 is a wiring diagram showing both the alternating-current connections and the directcurrent connections of a simplified relaying and telemetering apparatus illustrative of the application of our invention, and

Fig. 2 is a schematic diagram of the direct current connections,

In Fig. 1, we have illustrated our invention as being applied to the protection of one end of a three-phase transmission-line section 3, the three phase-conductors being distinguished by the letters A, Band C. The line-section 3 is connected, through a circuit breaker 4, to a bus 5, which is energized, through delta-star stepup transformers 6, from a generator-bus or supply-line 1.

Various line-responsive relays are provided,

which are supplied with energy by means of a bank of line-current transformers 8 which produce the relaying currents IA, In and I0, corresponding to the three-line-phases; a bank of auxiliary current-transformers 9, which produce the relaying currents (IAIB), (IB-I), (Io- IA); a bank of potential transformers ID, for supplying the relaying voltages; and a residual current-transformer l I which is connected in the grounded neutral of the line-connected star-side of the power-transformers 6, for obtaining a convenient source of reference-current for determining the direction of the residual line-currents, as will be subsequently described.

The circuit breaker 4 is provided with a tripcoil TC, which is energized, in accordance with the protective relaying means (subsequently described), through an auxiliary breaker-switch 4a, and a direct-current source which is symbolized by the battery-terminals and Our invention is illustrated as being applied to a relaying system of a type utilizing a number of phase-fault impedance-relays in each phase, said relays being of increasing sensitivities corresponding to what is known as first-zone," second-zone and third-zone operation, the different zones being indicated by the numerals I, 2 and 3, and the diiierent phases being distinguished by the letters A, B and C. As this type of relaying-system is well known, it has not been shown in its entirety, but we have selected the second and third-zone impedance relays to illustrate our invention, as indicated at ZZA, ZZB, Z20, Z3A, Z313 and 230. Each impedance-relay element consists of a voltage-responsive restraining-coil l2 and a current-responsive operatingcoil I3, suitably energized, in any desired manner, so that the relay is responsive to the line-impedance.

The' illustrated relaying-system also utilizes phase-fault-responsive directional elements, which are represented by the elements DA, DE,

and DC, a residual-current directional element Do, and a number of ground-fault detector-elements of different sensitivities, represented by the elements I02 and I03, the latter being the more sensitive.

The third-zone phase-fault impedance-elemerits Z3A, Z318 and Z are each provided with a make-contact and a break-contact, these contacts being sufficiently identified by the relay-designation, such as Z3A, etc. All of the other protective relaying elements thus far described are provided with a single make-contact apiece, these contacts being sufificiently identified by reference to the relay-designation, such as Z2A, etc.

The illustrated relaying-system also utilizes the previously mentioned auxiliary protective-relay contactor-switches CSA, CSB and CSC, one for each phase, and three timer-switches Ta, Tb and To. Each of' the contactor-switches GSA, CSB and CSC is provided with two make-contacts I4 and I5, the latter being utilized to control the secondary circuit of an auxiliary saturated current-transformer [6 which supplies the operatingcurrent for the timer-switch for that phase, as plainly indicated in Fig. 1.

The particular energizing-connections for the fault and directionally responsive relays and the timers, as illustrated in Fig. 1, include the energization of the third-zone operating-coils [3 in response to the line-current, and the energization of the second-zone operating-coils III in re sponse to the delta-current, the appropriate phases being chosen, in each case. In order to simplify the description, the phase-A connections will be described, and it is believed that the c0nnections for the other two phases will be readily understood from such description, in connection with the drawing. The Z3A operating-coil I3 is energized in response to the line-current IA, said coil being interposed between the phase-A linecurrent transformer 8 and a neutral conductor ll. The energizing-transformer l6 for the phase-A timer Ta is also illustrated as being ener gized in response to the phase-A relaying-current, in series with the Z3A operating-coil IS. The circuits for the phase-B and phase-C relayingcurrents also terminate in the neutral conductor ll, so that the residual or zero-phase-sequence currents flow through this neutral conductor, and are then supplied to the three ground-fault relays I03, I02 and Do, the circuit being completed with neutral conductor [6 of the star-connected line-current transformers 8. The polarizing winding of th ground-directional element Do is illustrated as being energized from the transformer-b and c grounded-neutral current-transformer i I.

The operating-coil l3 of the ZZA relay, and the directional-winding terminals of the phase-directional relay DA, are shown as being energized responsively to the delta-current (IA-IE) supplied from the auxiliary transformers 9, the various phases of the delta relaying-currents termiating with a star-point connnection l8. While one particular type of relay-energization, and relay-response, has been illustrated, it is to be understood that our invention is not limited to the precise type of relay.

The relaying system also includes a carriercurrent transmitter 2| (Fig. 1) which comprises an oscillator-tube 22, illustrated as comprising a cathode 23. a grid 24 and an anode or plate 26. The cathode 23 is connected to a cathode-circuit 21 which is adapted to be connected to the negative battery-terminal through the faultresponsive relaying-equipment, the circuits of which will be subsequently described. The anode 26 is connected to a source of. positive potential, indicated as being a tap 39 on a potentiometer 3| which is energized across the battery-terminals and In addition to the carrier-current transmitter, we also provide a carrier-current receiver 32 (Fig. 1), which comprises a receiver-tube 33, illustrated as comprising a cathode 34, a grid 35 and an anode or plate 36. The receiver-cathode 34 is connected, at 37, to a suitable source of negative potential, indicated as being a tap on the potentiometer 3i. The receiver-anode 36 is connected to a plate-circuit 38 which is, in turn, connected to one terminal of a holding-coil RRH of a receiver-relay RR, the other terminal of the holding-coil being connected to the positive battery-terminal through the telemetering or other-uses receiver-equipment marked TV relays, as indicated at 38'.

The receiver-relay RR is illustrated as a polarized relay having a tripping-coil RRT for energizing it in a direction to close its two contacts 39 and 40, this tripping-coil RRT being not as strong as the holding coil HRH, so that the receiver-relay will not respond to the tripping coil RRT unless the holding coil BBB is substantially deenergized. The two receiver-relay contacts 38 and 40 have a common terminal 4!, which constitutes the tripping-circuit of the circuit-breaker stantly energizes the receiver-relay holding-coil RRH, and thus prevents the receiver-relay RR from responding to any closing-impulse of its tripping-coil RRT. At either end of the protected line-section, where the fault-current is accompanied by an internal direction, one of the auxiliary directional relays CS? or CSG will respond, opening its back-contacts, thus interrupting carrier-current transmission at that end, and simultaneously energizing the receiver-relay tripcoil RRT, at that station. If the fault-current d notion is an into-the-line-looking direction at both ends of the protected section, carrier will be removed from both ends, and the receiver-relay holding-coilsRRH will be deenergized, permitting both receiver-relays RR to respond and complete as a tripping circuit through their contact 39 st, according as the fault is a ground-fault or a phase-fault.

The operating-coil X4 does not interfere with the transmitter-operation, because it is a lowimpedance coil which is energized through the resistance RI and the current through the oscillator-cathode 255, and it brings the potential of the oscillator-cathode 23 close enough to the potential of the negative bus to insure reliable carrier-transmission operation, whenever carriercurrent transmission is initiated by one of the sensitive faultdetectors 23A, ZSB, 23C or I03. As soon as the X4 relay is energized, in response to a fault-detector initiation of carrier-current transmission, it immediately picks up its makecontact K t, and connects the coils of the three contactor-switches CSA, CS3 and CSC, with their respective resistors RA, RB and RC, between the carrier-initiating bus A and the positive bus so that whichever one of these three contactorswitches is released for operation, by the opening of the shunt-connected back contact of the corresponding relay 23A, ZSB, or Z30, will immediately pick up and operate, so as to close its two front-contacts l4 and I5, the contact M being utilized to by-pass the sensitive fault-detector contact 23A, or the like, while the other contact it": is utilized to initiate the operation of the corresponding timer Ta, Tb, or To, as the case may be. Other uses are commonly made of the contactswitches USA, 053 and 080, but the uses which have been shown are deemed sufficient for the purpose of illustrating the principles involved. It Will thus be observed that our added relay X4 makes it possible to utilize the auxiliary protective relays GSA, 05513 and CS0 so as to operate practically as in previous conditions when the X 3 relay was not utilized. The addition of the X5; relay results only in a very brief and inconsequential time-hesitation, required for the response of this fast-operating relay.

From the standpoint of telemetering, or, in general, other uses of the carrier-current channel, the added X4 relay is of considerable impcrtance, in normally disconnecting the operat-' lug-coils of the three primary protective relays GSA, CS3 and CS0 from the carrier-initiating bus 1$, so that, when the telemetering key TV is operated, it will not be burdened with the current drawn by the three resistors RA, RB, and RC. In this manner, we have been enabled to considerably increase the life of the telemetering key TV without in the least impairing the effective operation of the protective relaying equipment. The carrier-current modulation effected by the telemetering key TV is responded to by the TV relays, as indicatedat 38.

While we have illustrated our invention in a preferred'form of embodiment, we desire it to be understood that this particular form of embodiment is only illustrative, in that our invention is susceptible of embodiment in other apparatus without departing from the essential spirit or principle of the novel features and operations which we have introduced. We desire, therefore, that the appended claims shall be accorded the broadest construction which is consistent with their language.

We claim as our invention:

1. A carrier-current protective relaying system, comprising the combination, with a transmission-line section having circuit-interrupting means to be protectively controlled, of protective relaying-apparatus including carrier-current transmitting and receiving-means coupled to the line-section, line-fault-responsive relaying-means for controlling both the carrier-current means and the circuit-interrupting means in a manner requiring a predeterminedly strong receipt of carrier to block erroneous circuit-interrupter operations under some fault-conditions involving faults on the transmission system but not in the protected 1ine-section, said line-fault-responsive relaying-means including means for initiating carrier-current transmission and means responsive to the same relay-operation for controlling a parallel-connected relay-apparatus which is connected in parallel-circuit relation to the transmission-initiating means, other-uses starting-and-stopping means for at times initiating carrier-current transmission in parallel-circuit relation to said transmission-initiating linefaultresponsive relaying-means, and an auxiliary protective relaying-means which is responsive to said transmission-initiating line-fault-responsive relaying-means, but which does not impose any material burden on the other-uses starting-and-stopping means, for disconnecting said parallel-connected relay-apparatus except upon the operation of said line-fault-responsive transmission-initiating means.

2. A carrier-current protective relaying system, comprising the combination, with a transmission-line section having circuit-interrupting means to be protectively controlled of protective relaying-apparatus including carrier-current transmitting and receiving-means coupled to the line-section, line-fault-responsive relaying-means for controlling both the carrier-current means and the circuit-interrupting means in a manner requiring a predeterminedly strong receipt of carrier to block erroneous circuit-interrupter operations under some fault-conditions involving faults on the transmission system but not in the pro tected line-section, said line-fault-responsive relaying-means including fault-detector means having a make-contact for energizing a carriertransmission-initiating relaying-circuit, a parallel-connected protective-relay apparatus connected for energization from the said carriertransmission-initiating relaying-circuit for operation in parallel-circuit relation to the controlled carrier-transmitter circuit, other-uses" circuitmake-and-break means for independently energizing the said carrier-transmission-initiating relayingcircuit, and an auxiliary protective-relaying-means which is responsive to said transmission-initiating line-fault-responsive relayingmeans, but which does not impose any material burden on the other-uses circuit-make-andbreak means, for disconnecting said parallel-connected relay-apparatus except upon the operation 2,367,921 I. for energizing the trip-coil TC through the auxiliary breaker-switch 4a, and the positive batten-terminal The various relaying-controls exercised by the line-responsive relays can now be described. The

contents of the ground-directional relay Do and an auxiliary ground-fault relay CSG, which is thus energized in response to a ground-fault which is accompanied by an inward direction of line-current-flow, such as will actuate the directional element Do.

A second relaying-circuit 43 is similarly enei gized in response to phase-faults, this relayingcircuit being energized through any one of three different channels, corresponding to the three line-phases A, B and C. Thus, in the phase-A channel, the energizing-circuit for the relayingconductor or bus 43 may be traced from the negative battery-terminal through the DA contact and the Z2A contact, to said relaying-circuit 43. One branch of th s relaying-circuit energizes the trip-circuit 4l through the second receiver-relay contact 40, while another branch of this relaying-circuit 43 energizes a directionally controlled phase-fault-responsive auxiliary relayCSP.

The fault-responsive carrier-current control is illustrated as including the operating-coil of an auxiliary protective relay X4, which is intended to be symbolic of any means which is selectively responsive to a fault-detector carrier-starting operation, without imposing a material burden on the telemetering key', as will be subsequently explained. The X4 coil is connected between the negative bus and a relaying-circuit 44, which is, in turn, connected to another relaying-circuit 45 through any one of six paths including the make contacts of the three third-zone impedance-elements Z3A, Z313, and 23C, and one of the contact l4 of each of the three auxiliary contactcr-switches CSA, CSB and CS0.

The relaying-circuit 45 is utilized, among other functions, to energize the cathode-circuit 2? ol the oscillator-tube 22, the connection between the circuit 45 and the circuit 21 being completed through the back-contacts of the two auxiliary directionally controlled relays CSP and CSG, so that carrier-current transmission can be interrupted, at any time, by an actuation of either one of these directionally controlled elements, opening one of th back-contacts CSP or CSG. It will be understood that carrier-current transmission is initiated by the response of one of the sensitive third-Zone phase-fault impedance-eleinents Z3A, Z3B or Z3C, which results in connecting the oscillator-cathode 23 to the negative bus through CSG and CSP contacts, the Z3 contact, and the X4 coil.

The oscillator-cathode circuit 27 is permanently connected to a positive source, such as the bus-terminal through a resistor Rl, so that carrier-current transmission is prevented by holding the oscillator-cathode 23 at a positive potential, rather than a negative potential, at all times except when a direct connection is made Ill Ill

from the cathode-circuit 21 to the negative source or bus.

Carrier-current transmission may also be initiated in response to ground-faults through the contact of the sensitive residual-current relay I03, which is connected between the relayingcircuit 44 and the intermediate point or circuit 48v between the CSP and CSG contacts. Inthis manner, carrier-current transmission can be started by making the oscillator-cathode 23 negative through a circuit including the CSG back contact, the I03 make-contact and the X4 coil, thus making it impossible for the phase-fault directionally controlled relay CSP to interrupt carrier which has been initiated by a ground fault response.

Carrier-current transmission can also be initiated and controlled by means of a telemetering key or contact TV and a resistor R2, which are connected between the negative battery-terminal and the relaying-circuit 45, the resist ance R2 being utilized so that the telemetering key TV will not short-circuit the X4 coil. The telemetering control of carrier may be traced from the oscillator-cathode circuit 21 through the CSG and CSP contacts to the relaying-cirsuit 45, and thence through the resistor R2 and the telemetering key TV to the negativ bus In addition to the carrier-starting function just described, the relaying-circuit 45 is utilized to energize the operating-coils of the three contractor-switches CSA, C513 and CS0, which are energized, in three separate circuits including the respective resistances RA, RB, and RC, which terminate in a relaying-circuit 41, which is connected to the positive bus (-t) through the contact of the auxiliary relay X4, The operatingcoil of each of the contactor-switches GSA, C813 and CS0 is normally by-passed by the back-contact of its corresponding third-zone impedanceelement Z3A, 23B or Z30, respectively, each for its own phase, so that only the contactor-switch will operate, corresponding to the phase which is faulted.

The receiver-relay trip-coil RRT is energized, in series with a resistance R3, between the relaying-circuit 45 and the oscillator-cathode circuit 21, so that th BET coil is normally short-circuited by the two back-contacts of the directionally responsive relays CSP and CSG, so that the energization of the trip-coil RRT of the receiverrelay RR is initiated by the same operation which interrupts carrier-current transmission by the opening of one of the auxiliary directional-relay back-contacts CSP or CSG.

In operation, except for the addition of the auxiliary relay X4 and its contact, the faultresponsive part of the equipment operates in a manner which is now common in this country. The system is one which requires carrier-current reception (in the energization of the receiver- 'relay holding-coil RRH), in order to prevent an erroneous tripping-operation in the event of a "through fault, or fault somewhere beyond the other end of the protected line-section 3. It will be understood that the protective equipment will be the same, or similar, at the two ends of the protected line-section, and that the two transmitters 2| will be tuned to the same carrier-current frequency, so that the receivers 33 and RR at both ends of the protected line-section will be energized if either transmitter is operating. When a fault occurs, a sensitive fault-detector, such as Z3A or I03, first initiates carrier-current transmission. The initiation of carrier-current transmission inof said line-fault-iresponsive transmission-initiating means. i v

3. A carrier-current protective relaying system, comprising the combination, with a transmission-line section having circuit-interrupting 5 means to be protectively controlled, of protective relaying-apparatus including carrier-current transmitting and receiving-means coupled to the line-section, line-fault-responsive relaying-means for controlling both the carrier-current means 10 and the circuit-interrupting means in a manner requiring a predeterminedly strong receipt of carrier to block erroneous circuit-interrupter operations under some fault-conditions involving faults on the transmission system but not in the protected line-section, said line-fault-responsive relaying-means including fault-detector means having a make-contact for energizing a 15 upon a response of said fault-detector means.

JOHN L. BLACKBURN. JAMES F. CHAPMAN. 

